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Mechanical properties and microstructures of steel panels for laminated composites in armoured vehicles


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This paper present the study about the mechanical properties of two high strength low alloy steels for replacing the current rolled homogeneous armour (RHA) for ballistic application. High strength low alloy steel has been widely adapted as a ballistic plate in light armoured vehicle. However, the current used RHA plate is very heavy thus restricted the manoeuvrability of the armoured vehicle. The aim of this study is to find materials suitable to be used for production of composite protection panel which is lighter yet has similar mechanical properties to RHA. The tensile strength and hardness of AISI 4340 and AR500 steels were evaluated and compared to that of RHA and the results were analysed based on its chemical compositions and microstructural observation. Values of these properties are primarily reflected by its microstructures and chemical compositions. Therefore, microscopic observation of microstructural arrangement and phases are essential in understanding the hardness and stress-strain behaviour of these metals. Results indicate similar tensile properties were observed in RHA and AR500 but different properties obtained for AISI 4340. Tensile strength of RHA and AR500 were 1750 MPa and 1740 MPa respectively followed by AISI 4340 at 1020 MPa. AISI 4340 steel exhibited the highest elongation at 20.6% compared to RHA and AR500 at 13.3 and 12.5%, respectively. Higher degree of carbon content in fine martensitic structure of RHA and AR500 led to high hardness. Imperfections in RHA and AR500 were also removed by hot rolling process as indicated by white banding that cause higher in tensile strength. Retained austenite and coarse microstructure of AISI 4340 steel contributed to higher ductility compared to AR500 and RHA. Therefore the tensile properties of RHA and AR500 were found similar due to its microstructure behaviour. This similarity allows AR500 to be utilised as alternatives to RHA in armour plate application.
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International Journal of Automotive and Mechanical Engineering (IJAME)
ISSN: 2229-8649 (Print); ISSN: 2180-1606 (Online);
Volume 13, Issue 3 pp. 3742 - 3753, December 2016
©Universiti Malaysia Pahang Publishing
Mechanical properties and microstructures of steel panels for laminated
composites in armoured vehicles
W.N.M. Jamil 1, M.A. Aripin 1, Z. Sajuri1,2,a, S. Abdullah1,2, M.Z. Omar1,2, M.F.
Abdullah1 and W.F.H. Zamri1
1Department of Mechanical and Materials Engineering,
Faculty of Engineering and Build Environment, Universiti Kebangsaan Malaysia
43600 UKM Bangi, Selangor, Malaysia.
2Centre for Automotive Research, Faculty of Engineering and Build Environment,
Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia.
This paper present the study about the mechanical properties of two high strength low
alloy steels for replacing the current rolled homogeneous armour (RHA) for ballistic
application. High strength low alloy steel has been widely adapted as a ballistic plate in
light armoured vehicle. However, the current used RHA plate is very heavy thus restricted
the manoeuvrability of the armoured vehicle. The aim of this study is to find materials
suitable to be used for production of composite protection panel which is lighter yet has
similar mechanical properties to RHA. The tensile strength and hardness of AISI 4340
and AR500 steels were evaluated and compared to that of RHA and the results were
analysed based on its chemical compositions and microstructural observation. Values of
these properties are primarily reflected by its microstructures and chemical compositions.
Therefore, microscopic observation of microstructural arrangement and phases are
essential in understanding the hardness and stress-strain behaviour of these metals.
Results indicate similar tensile properties were observed in RHA and AR500 but different
properties obtained for AISI 4340. Tensile strength of RHA and AR500 were 1750 MPa
and 1740 MPa respectively followed by AISI 4340 at 1020 MPa. AISI 4340 steel
exhibited the highest elongation at 20.6% compared to RHA and AR500 at 13.3 and
12.5%, respectively. Higher degree of carbon content in fine martensitic structure of RHA
and AR500 led to high hardness. Imperfections in RHA and AR500 were also removed
by hot rolling process as indicated by white banding that cause higher in tensile strength.
Retained austenite and coarse microstructure of AISI 4340 steel contributed to higher
ductility compared to AR500 and RHA. Therefore the tensile properties of RHA and
AR500 were found similar due to its microstructure behaviour. This similarity allows
AR500 to be utilised as alternatives to RHA in armour plate application.
Keywords: High strength steel; tensile strength; ductility; hardness; martensitic.
Various materials especially metals, ceramics, polymers, and composites have been
utilised in light vehicle defence technology. With each material appearing significant in
respective applications, metals are mostly utilised for ballistic protection due to its
mechanical properties. Therefore metals of high tensile, hardness, and ductility were
numerously proposed as a ballistic protection plate [1-5]. Based on mechanics of
Jamil et al. / International Journal of Automotive and Mechanical Engineering 13(3) 2016 3742-3753
projectile impact, the penetration of bullets depends on many factors that occur over three
phases namely the initial impact phase, stress propagation phase, and fracture initiation
phase [6]. During initial impact phase, the projectile kinetic energy is converted in impact
energy on the surface or steel plate [7]. The massive force that acts on the plate can be
reduced by increasing the hardness of the plate [8]. Once the hardness of the plate is
higher than projectile tips, the projectile will shatter and kinetic energy of bullet would
be reduced proportionally to its mass [6]. Development of hard protection plate goes back
in the 1980s prior to its contribution to penetration resistance. However, hardness
increment is only effective up to critical limit because it promotes brittleness in plate that
leads to shattering effect [9]. If a protection plate is not hard enough, a projectile tip made
from high hardness material with sufficient kinetic energy can penetrate the plate. During
impact, balance kinetic energy from projectile exerts large deformation and stress wave
on plate over a short period of time. The ability of the plate material to resist bullet
perforation depends on the tensile strength [10] where good energy absorption capacity
is needed in order to deform the projectiles tips [11]. Moreover, stress wave continues to
propagate until the rear side and reflects the waves upon the backplate causing
fragmentation of brittle metal (spalling effect). Therefore it is essential for protection plate
to have sufficient ductility. This allows plate to bend so it can absorb the stress of impact
at high velocity without shattering [12, 13].
Current light vehicle armour used by Malaysia Armed Forces, SIBMAS is utilising
monolithic rolled homogenous armour (RHA) as its protection panel as shown in
Figure 1. However, the thick monolithic panel is heavy and causes limitations on vehicle
mobility. Therefore weight reduction approach has been implied towards protection panel
design. One of the most common methods for weight reduction while maintaining its
strength is to embrace composite protection panel. The design of laminate must retain the
original strength, while reducing the weight of panel [14-16]. As studied, the front
material of protection panel must consist of high hardness, whilst the back plate has high
ductility. Die to this reason, it is essential to identify the alternative front metal panel to
replace the RHA. The protective panel of light armour vehicle will experience mainly
ballistic and bending load. Therefore the alternative replacement must be evaluated as per
actual condition. But the preliminary study must be limited on basic mechanical
properties, such as tensile and hardness of the metal. The tensile strength and hardness of
metal relies on several factors but primarily the microstructure. The final microstructure
of material is a result of series of heat treatment. Heat treatment can be categorized by
austenizing, quenching and tempering.
Tempered martensitic matrix contributes higher hardness as the decreasing of
grain size by carbon precipitation [17]. The effectiveness of tempering is further
supported by [18] in his study which reveals that high hardness is obtained when
tempering of amour material was done at 200 °C due to the stress relief annealing effect.
Grain boundary effect has been studied by [19] where smaller grain size increases tensile
strength. Other than that, tempered bainite steel was reported to exhibit superior hardness
and toughness when contacting armour piercing 7.62 mm caliber projectile [20]. Also,
the percentages of alloying elements are very important for precipitating carbide particles.
With proper heat treatment process, the precipitation of carbide particles can contribute
to high strength in the steel structure [21]. It is also noticed that boron, carbon, manganese,
and nickel elements play a main role to improve ballistic properties of armour material
[22]. In this study, mechanical properties of three different steels i.e. AISI4340, RHA,
and AR500 are compared by tensile and hardness test. The result obtained will be
analysed based on its microstructural and composition properties. The purpose of the
Mechanical properties and microstructures of steel panels for laminated composites in armoured vehicles
present work is to preliminarily evaluate the tensile strength, ductility, and hardness of
the high strength low alloy steel as alternative front panels to replace the existing RHA.
The findings for this paper will benefit as base study for metal selection in future test
which includes bending and ballistic testing.
Material Selection
The materials used in this study were three types of high strength low alloy steel suitable
for ballistic application namely rolled homogenous armour (RHA) steel, ABREX
abrasion-resistant steel (AR500), and AISI 4340 steel plate [23-25]. RHA is most
commonly utilised on high strength steel in armoured vehicles due to its high tensile
strength and toughness. The RHA steel used in this study was taken from the door of a
6x6 infantry fighting vehicle of the Malaysian Armed Forces, SIBMAS AFSV-90
armoured vehicle as shown in Figure 1. Besides RHA, AR500 and AISI 4340 are gaining
popularity due to their lightweight properties. AR500 is specifically known for its
abrasion resistant properties and AISI 4340 has a well balance tensile, toughness, and
wear resistance according to local manufacturers.
(a) (b) (c)
Figure 1. High strength low alloy steel for ballistic application (a) SIBMAS
(b) monolithic panel utilised currently (c) proposed laminated panel.
Experimental Procedure
Specimens for microstructure, spectrometer elemental analysis, hardness, and tensile tests
were cut using Fanuc C400iA EDM wire cut so that the analysed cross section surfaces
were in perpendicular direction to the rolling direction of the rolled plate as shown in
Figure 2. The dimension of spectrometer analysis and microstructure specimen was 10
mm × 10 mm × 10 mm. METEX spectrometer was used to identify the percentage of
alloying elements in all steels with three times repetition in order to obtain accurate data.
Then, for microstructure specimen were grinded from 240, 400, 800, and 1200 grit of SiC
sand papers before being polished using 3- and 6-micron diamond suspensions to get a
mirror-like surface. Nital (3% HNO3) was used for etching to reveal the microstructure.
The specimens are pictured with magnification ×50 using optical microscope for
metallographic examinations.
Figure 3(a) shows the size and dimension of tensile test specimen. Specimen was
prepared based on the ASTM E8. The cross section and the length of the gauge area were
6×6 mm2 and 25 mm, respectively. Tensile test was performed on a Zwick Roell Z100
Jamil et al. / International Journal of Automotive and Mechanical Engineering 13(3) 2016 3742-3753
universal testing machine of 100kN capacity as shown in Figure 3(b). Sample was
strained at a cross head speed of 1.5 mm/min to obtain the stress-strain curve for
mechanical properties analysis. In measuring the hardness of the tested materials,
Rockwell hardness tester of Shimadzu was used for C scale hardness measurement as
shown in Figure 4. Indentations were performed on three points to get an average hardness
Figure 2. Specimen cutting from rolled plate.
Figure 3. (a) Tensile test sample size and dimension, and (b) tensile testing
Mechanical properties and microstructures of steel panels for laminated composites in armoured vehicles
Figure 4. Hardness test using Shimadzu.
Alloying Elements
Table 1 shows the chemical composition of RHA, AISI 4340, and AR500. Composition
comparison was highlighted between RHA and AR500 since both steels were heat treated
to martensitic phase prior to ballistic requirement. Carbon content in AR500 was found
higher than that in RHA. Apart from carbon, AR500 also exceed in manganese and boron
compared to other steels, whilst RHA has higher content of nickel compared to AR500.
On the other hand, AISI 4340 has exceptionally high content of Nickel compared to in
RHA and AR500.
Table 1. Chemical composition of AISI 4340, RHA and AR500 using spectrometer (wt-
The ballistic performance of armour steel depends on the matrix having tempered
martensitic or bainitic structure [22]. This is achieved after application of austenisation,
quenching, and tempering on low alloyed steel of AISI 4340, RHA, and AR500 [24-26].
After the process of austenisation and quenching, crystal structure of steel is changed
from austenite Face Centered Cubic structure (FCC) into carbon supersaturated Body
Centered Tetragonal structure (BCT) to form martensitic or bainitic structure [27]. Then
heat treatment of tempering will develop the strength and toughness of the matrix
consisting of tempered bainite or martensite [28]. Microstructures of all the low alloy
steel plates are given in Figure 5. AISI 4340 steel exhibits coarser grains in bainite phase.
Jamil et al. / International Journal of Automotive and Mechanical Engineering 13(3) 2016 3742-3753
Bainite consists of lath type ferrite and precipitates within ferrite phase and at the
boundaries of the laths [29]. Apart from that AISI, 4340 also has increments in retaining
austenite as shown in Figure 5(a). Existence of retained austenite is caused by the
imperfection during heat treatment process. The retained austenite presence is believed
due to the non-uniformity of temperature and cooling rate, where the transformation of
austenite phase to bainite phase was not complete uniformly [30]. In addition, retained
austenite is a softer phase compared to the martensite, hence the hardness of the material
will be reduced [2]. This retained austenite can decrease the strength to defend against the
bullet. As shown in Figure 5(b), RHA steel revealed a tempered martensitic phase.
Carbide precipitates were observed disperse in the matrix as well. Similar to RHA, AR500
exhibits fine structure and in tempered martensitic phase in Figure 5(c). Tempered
martensite consists of recovery and recrystallisation in the matrix to relieve the stress
generated during the quenching process [31]. Matrix phase is changed because the carbon
atoms move out from the matrix in order to form carbide precipitates [32]. Other than
that, banding effect appeared in white shade was captured in the present study. This
banding effect is formed due to rolling process. The process of rolling involves cast steel
billets of appropriate size and then rolling them into plates of required thickness [33]. Hot
rolling changes the coarse grain into the finer grain sizes and increases the mechanical
properties [34].
(a) RHA (b) AISI 4340
(c) AR500
Figure 5. Optical microscopy observation of microstructures in (a) RHA (b) AISI
4340, and (c) AR500.
Mechanical properties and microstructures of steel panels for laminated composites in armoured vehicles
Tensile Test Analysis
The tensile test results are shown in Figure 6 and summarised in Table 2. Figure 7 shows
the bar chart that indicates the error and uncertainty for tensile test value measurement,
based on standard deviation and average repetition during experiment. According to the
stress-strain curves shown in Figure 6, RHA exhibits the highest tensile strength of 1750
MPa, closely followed by AR500 at 1740 MPa. AISI 4340 recorded lowest tensile at 1020
MPa. This value is 41% lower compared to RHA. The phases in the high strength low
alloy steels are believed the main contributing factors for determining the tensile strength
of the materials. As seen in Figure 5(b) and 5(c), both RHA and AR500 consist of
tempered martensitic phase, reflecting to similar tensile strength values of RHA and
Nickel is believed to be the main alloying element responsible to increase the strength
of steel besides carbon that still maintains its role as a strengthening mechanism [18].
Comparing the chemical compositions, RHA has higher content of nickel compared to
AR500. [21] reported that during the tempering process, steel solution rejects carbon in
the form of finely divided carbide phases, the high supersaturated solid solution of carbon
in iron forming a martensitic microstructure. The final result from the tempering process
is a fine dispersion of carbides in an α-iron matrix. Precipitates of carbide particles are
present in high strength steel [21], having the black particles as iron carbide. During the
tempering process, martensite is decomposed to form carbide particles [35]. This is due
to the carbon atoms travelling out of the spaces between the iron atoms [36]. The strain
in the martensite is relieved as the carbon atoms leave the matrix. This behaviour
contributes to higher strength and hardness [37]. Therefore, it is observable in RHA
microstructure tempered martensite with very small iron carbide islands which results in
high tensile strength. This is similar to observation made by [38].
Figure 6. Stress-strain curves for RHA, AISI 4340 and AR500 steels.
The tensile strength of both RHA and AR500 can be further increased by hot
rolling process. Hot rolling was performed to homogenise the grain structure of the steel,
removing imperfections which would reduce the strength of the steel. Rolling also
elongates the grain structure in the steel to form long lines, which enables the stress under
which the steel is placed when loaded to flow throughout the metal, and not be
concentrated into one area. This can be seen by white banding effect in Figure 5(b-c).
0 5 10 15 20 25
Stress (Mpa)
Elongation (%)
Jamil et al. / International Journal of Automotive and Mechanical Engineering 13(3) 2016 3742-3753
Consequently, both alloys resist stress higher than ordinary steel. Strength increment can
finally be increased by resisting dislocations at grain boundaries. Therefore higher
amount of grain boundaries in an area resulted in higher strength since it acted as pinning
points [39]. This is reflected by RHA fine microstructure, similar to AR500. Based on
the study on the impact on steel made by [40], they indicated the potential of RHA and
AR500 used as single impact steels with tensile strength, yield strength, and strain falls
in the range of 1650-2050 MPa, 1200-1370 MPa and 12-24% respectively.
Meanwhile, RHA and AR500 tops of the tensile strengths AISI 4340 steel exhibit
highest elongation at 20.6%, compared to RHA and AR500 at 13.3% and 12.5%,
respectively. Based on the microstructure shown at Figure 5(a), AISI 4340 has a bainitic
phase with retain austenite appears as white block. Austenite is softer than bainite and
martensite. Therefore as reported by [30], the increment of retained austenite reduces
hardness and increase ductility of AISI 4340. Apart from that, although a majority
element increases strength, nickel was among the few elements that balance the ductility
and toughness of the metal. Consequently, the amount of nickel is highest in AISI 4340
as highlighted in Table 1.
Figure 7. Error bar chart for AISI 4340, RHA and AR500 steels.
Hardness Test Result
The values of hardness are compiled and shown in Table 2. Referring to the hardness
properties, AR500 recorded the highest hardness at 47.3 HRC compared to RHA at 43
HRC and AISI 4340 at 34 HRC. There are several factors that contribute to hardness
increment primarily its microstructure phase. Hardenability was adequate to achieve by
high percentage of martensite [24]. As seen in Figure 5(b) and 5(c), RHA and AR 500
consist of fully martensitic phase. According to the study by [22, 41, 42], martensitic
transformation process for RHA and AR500 was enhanced by manganese due to
decrement of critical quench speed. Manganese was found to be highest in AR500. Apart
from manganese, boron also controls martensitic transformation by preventing bainite
and pearlite transformation evidently the amount of boron in AR500 is higher than RHA.
Since RHA steel microstructure is also in martensite phase, further hardness of martensite
is solely dependent on carbon content.
Elongation (%)
Strength (MPa)
Tensile Strength
Yield strength
Mechanical properties and microstructures of steel panels for laminated composites in armoured vehicles
Table 2. Mechanical properties of RHA, AISI 4340 and AR500 steels.
AISI 4340
Carbon is a very small interstitial atom that tends to fit into clusters of iron
atoms. It strengthens steel and gives it the ability to harden by heat treatment particularly
if it exceeds 0.25%. Carbon forms compounds with other elements called carbides, such
as cementite, exist as precipitate and increase hardness which is mentioned in finding by
[43] and [44]. Similar to spectrometer result, carbon content in AR500 was higher than
RHA. Consequently, higher hardness could be achieved, as reported by [24]. Besides
interstitial carbon that resists slippage, grain boundary also acts as a pinning point to resist
dislocations. Fine microstructure as shown in Figure 5(b) and 5(c) consisting of high
number of grain boundary in constant area increases resistance to slippage, which
improves both tensile strength and hardness. AR500 and RHA represent a tiny of grain
boundary that appears invisible. This is also reported by [10] where transformed band
produces fine structure increases hardness.
In this study, the mechanical properties and microstructures of three high strength low
alloy steels were investigated. Tensile properties of RHA were found similar to AR500
steel but different from AISI 4340. Tensile strength of RHA, AR500, and AISI 4340 were
1750, 1740 MPa, and 1020 MPa, respectively. Comparing all alloys, AISI 4340 steel
showed the highest elongation at 20.6% followed by RHA and AR500 at 13.3 and 12.5%,
respectively. RHA and AR500 showed tempered martensitic matrices that contribute to
higher hardness due to higher amount of carbon content in martensitic structure. Retained
austenite and coarse microstructure of AISI 4340 steel contributed to higher ductility
compared to AR500 and RHA. RHA and AR500 exhibited similar tensile properties with
higher tensile strength and yield strength compared to AISI 4340. Finer microstructure
and full martensite phase in RHA and AR500 contributed to higher hardness and strength.
Coarse grain and retain austenite reduced hardness of AISI 4340. The compositional and
microstructural effects on mechanical response provide insights in steel armour metal
processing. It is concluded that AR500 has a potential to be used to replace RHA as an
impact front panel steel for ballistic application.
The authors would like to express their gratitude to the Universiti Kebangsaan Malaysia
(UKM) and Universiti Pertahanan National Malaysia (UPNM) for the research facilities
and supports, and Ministry of Higher Education Malaysia for the research fund
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... Brief austenization on one side of the plate surfaces and immersion in oil can change the surface hardness on one side of the plate, while the hardness of the other sides of the plates is maintained from the raw material. According to [17] [18], the hardness value which is capable of resisting the ballistic speed is around 450 HV, so this result is still unable to resist the projectile speed. The average tensile strength of raw materials and the variety in austenization temperature are shown in Figure 7. Figure 7. Graph a). ...
... The highest maximum tensile strength value is achieved in samples at 900 o C austenization temperature of 900 MPa. This value has not been able to hold the projectile rate of 1750 MPa [17]. The test on impact value of the HB500 bullet proof plate showed the result of 0.43 J/mm 2 [19]. ...
... PT, and the substrate material is steel (AISI 4340). The material properties of PMN-0.33 PT are given in [45]. PMN-0.33 PT has a thickness of 0.191 mm, a cavity height of 1.5 mm, and an end cap thickness of 1.5 mm. ...
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Cymbal transducers have been discovered as a viable design for piezoelectric energy harvesting under heavy impact loads. However, low-output voltage remains a source of concern; therefore, many promising approaches for enhancing performance efficiency are crucial in the field of piezoelectricity. This study presents a viable angular poling approach for flex tensional based cymbal structures solely for energy harvesting applications. Elementary and Euler angular poling are two types of angular poling introduced for cymbal piezoelectric transducers. Using the energy method, theoretical modelling is performed on a cymbal structure exposed to a 1000 N impact force. Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-0.33 PT) is utilised as a piezoelectric material because of its strong piezoelectric properties in both tetragonal and rhombohedral symmetry. The findings show that Euler angular poling outperforms elementary angular poling due to its reliance on two angles. When elementary angular poling is used, the voltage and energy reach 108.9 V and 380.1 μJ, respectively, resulting in a 198.02% and 2800% enhancement over the original PMN-0.33PT material. Similarly, in Euler angular poling, voltage and energy reached 123.59 V and 450 μJ, respectively, resulting in increase of 238.1% and 3340%. Finally, potential applications include powering light-emitting diodes and charging small portable electronic devices such as digital cameras and cell phones. A large-scale system can be built using cymbal piezoelectric tiles, making it suitable for use in industrial applications such as ultrasonic welding, diesel fuel injectors, and robotic systems.
... Grain particles are seldom irregularly distributed throughout the material composition. The mechanical properties of metal matrixes are strongly dependent on grain size (Jamil et al., 2016). From studies at low temperature, 25 % of the grain size decreases the strength of alloys consequently with ductility reduction (Barba et al., 2020). ...
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The study discusses an overview of small rocket program, development and characterization of locally sourced material at low cost. The aim is to enable the construction of small sounding rocket components for experimental purposes in Nigeria. This paper proposes the utilization of palm kernel shell ash as filler materials in the development, characterization and production of composite material to construct prototype reusable chamber and accessories that will enable it possible for small scientific experiments. To achieve this, particle size and particle range distribution on the microstructure, texture, and mechanical properties of (Al–Mg–Si)/PKSA composites developed by powder metallurgy method were investigated. The access in the 6xxx series of aluminum-magnesium-silicon alloy was investigated for this reason. ImageJ software was used to do particle size analysis professionally and the software was used to calculate the area, mean, standard deviation (SD) and the pixel values. The particle size distribution of big constituent (densification or rather densified solids) particles and small dispersoids possess a finer and slightly elongated grain structure when compared with the unreinforced alloy. The results of the XRD and XRF of all the samples considered showed that Al2O3, SiO2, Mn2O3 and MgO phases were common to all. These hard phases are considered to be responsible for improved mechanical properties and resistance of the composite, while the SEM result showed that the reinforcement was uniformly distributed which further improves the mechanical property of the composite.Keywords: Microstructure, Composite, Rocket, Palm Kernel
... Like trains and airplanes, manufacturers of passenger and military transport, such as lightweight armoured vehicles, are interested in enhancing vehicle performance through the use of sandwich panels in most of the vehicle parts manufacturing process [6,10,11]. Recent research shows that the application of sandwich structure into the body panel of vehicle by enhancing the structure with multilayered plates instead of single monolithic panel may reduce the weight of the vehicle by at least 30% from the overall weight without losing the structural integrity and increase the ballistic limit of that structure [12][13][14]. ...
This review outlines the evolution of sandwich panels based on recent work and older sources, focusing on the trends concerning sandwich panel achievements and applications, core materials, core designs, types of failure mechanism and factors which contribute to the failure of sandwich panel. The review begins with an extensive discussion highlighting the achievements and trends relating to sandwich panels over the past 50 years, including the most recent work published. The purpose of this paper is to re-evaluate the current core design of metal-based sandwich panels, and further elucidate on core design, core materials and the types of failure mechanism which sandwich panels usually experience under certain conditions. The main factors that contribute to the failure phenomena experienced by sandwich panels, such as geometries of core design, different configuration of core design, the adhesive interaction effect between the bonding layers of sandwich panels and the effect of sandwich panels under high-speed impact and blast loading are considered. Future issues regarding metal-based sandwich panel, including the use of new materials for the core, new concepts in core design and the possibility to extend sandwich panel use for heavier applications, such as the defence industry, are highlighted and discussed. At the end of this review, the authors draw attention to other researchers by suggesting a list of topic areas that need to be addressed by research in the near future.
... The achieved results of the research published in the authors' articles [1][2][3] as well as the knowledge obtained from industrial practice show the need to evaluate the surface conditions of these parts as the result of a particular technological process depending on specific operating conditions of the surface in operation. It is precisely this view of surface assessment that is often referred to as surface integrity. ...
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This authors presented article deals with the size of heat affected zone (HAZ) at specific technological processes (cutting and welding techniques). Armox 500 steel was selected and used to perform all realized experiments. Even before the start of the experiments that investigated the effect of HAZ on cutting and welding, it was necessary to subject the investigated Armox 500 steel to basic experimental measurements with regard to its chemical composition, fundamental microstructure and mechanical properties. The microstructure was performed on Neophot 32 optical microscope. Chemical composition was analysed on the spectral analyzer Spectrolab Jr CCD. Mechanical properties, like nanohardness H and reduced Young modulus Er were subsequently measured on Hysitron TI950 Triboindenter with a Cube Corner measuring tip, and evaluated by software Triboscan. Based on the measured values, a 2D nanostructure of the distribution map of s H and Er was evaluated in Matlab. This scientific research, together with all measured and calculated results, is the fundamental that will help to optimizing the quality and used all these results to optimize presented material and technological processes.
This research studied the characteristics of fatigue and Crack Growth (CG) behaviour of AZ31B magnesium alloy at room temperature when the material was used for designing. The experiments were carried out using a fatigue machine, which involved the experimental testing of stress–strain material and fatigue and CG tests. The fatigue test was conducted using a standard ASTM E8 and dog bone samples at 90, 80, 70, 60 and 50% of applied yield stress. Meanwhile, a CG test was done using ASTM E647 standard Compact Tension (CT) and specimen at 90% of yield stress. Both tests were conducted under a sinusoidal cycle by applying the Constant Amplitude Loading (CAL) at a frequency of 10 Hz. The fatigue endurance showed that at 1 × 106, the stress was 48 Mpa using the Basquin equation prediction. The predicted lives were in good agreement with an R2 of 0.91. The CG behaviour of the specimen, indicating a fatigue CG (a-N) with failure of the structure, and the Paris Law constants were determined.
Background:Battle of weapon and armor has been continuing from the beginning of the human history. As new weapons are developed, in response to that corresponding armors are been developing. Even Today, development of lightweight armors against kinetic energy caliber projectiles is getting important as mobility is considered. In this work, study regarding the effect of projectile on group of armor and ballistic protection efficiency is performed. The interaction between the kinetic energy projectile and armor plate falls into the domain of terminal ballistics science. Materials and Methods: In this work, set of two different composite armors consisting of Steel, Dyneema, Kevlar, Ceramic materials are of optimized configurations are procured to test against the standard 7.62mm projectile in a 90 degrees angle at normal laboratory conditions of ballistic experiment. Results: Dynamic analysis results helped us to know the stress and stain patterns over the armor system and how energy in armor layers comes down to zero. At the same time investigation of energy losses, reduction of bullet velocity in armor layers is carried out to define the armor stability and performance. Conclusion: Material properties and thickness of armor layers finalized from various journal papers are in good concurrence with the results obtained from experimentation.
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Induction hardening serves as one of the best mass production processes used recently due to its ability to quickly generate high-intensity heat in a well-defined location of the part. Numerous advantages of this method make it a reliable technique to produce a thin martensite layer on the part surface that has compressive residual stresses. In this regard, the presented study is devoted to investigating utilizing induction heating for surface hardening of AISI 4340 steel disc. The purpose is to evaluate the performance of magnetic flux concentrators and the effects of the induction process parameter on the case-depth and edge effect in the surface hardening of the disc. Once the proper range of parameters is defined, Taguchi experimentation planning is used to frame comprehensive experimentation with the minimum possible trial. Then, the case-depth of discs is evaluated on their cross-sections (edge and middle plane) through hardness profile measurement of samples using a micro-indentation hardness machine. The results are then statistically analyzed using analysis of variance (ANOVA) and response surface methodology (RSM) to determine the best combination of parameters to achieve maximum case-depth yet minimum edge effect. The goodness-of-fit regression models are then developed to predict the case-depth profile as a function of machine parameters based on linear regression utilizing case-depth responses in the edge and middle planes of discs. Results imply that maximum case-depth with minimum edge effect can be produced by using the highest heating time along with the average amplitude of the power, axial gap, and radial gap. This study gives a good exploration of case-depths optimized by setting up process parameters when a magnetic flux concentrator is utilized; thus, a guideline to reduce discs edge effect in induction surface hardening application is given.
The development of advanced small caliber weapon systems has resulted in rounds with more material penetration capabilities. The increased capabilities may mean that existing live-fire facilities will no longer be adequate for the training and certification of military and law enforcement personnel. Constraints on training in many live-fire shoot house facilities are already in place, with some allowing only single round impact during training. With little understanding of the probability of perforation, or failure, of existing containment systems, this study evaluates risk by studying the single round impact of small caliber ammunition against live-fire shoot house containment systems constructed from AR500 steel panels with two-inch ballistic rubber covering. An analytical and numerical study was conducted using an existing model for steel penetration developed by Alekseevskii-Tate and the EPIC finite element code. A modified form of the advancing cavity model for the ballistic resistance of the target material was used to account for the relatively unconfined material resulting from the studied impacts. These results are then compared to experimental tests conducted by Goodman for rounds of various small calibers impacting live-fire facility containment systems. Projectile and target characteristics were then modeled as continuous random variables, and Monte Carlo simulations were conducted using the validated analytical model to estimate the probability of a single round impact perforating the live-fire facility containment system. An importance sampling scheme was used to reduce the variance of the solution and provide a more accurate estimate of the probability of failure. The Alekseevskii-Tate model was found to provide accurate estimates of the depth of penetration when compared to experimental and numerical results at ordnance velocities and an estimate of the probability of failure is on the order of 1x10 ⁻⁵ . This study provides useful tools for the analysis of existing live-fire facilities against future and existing ammunition, and for the design of new facilities. When coupled with Monte Carlo simulation techniques, a risk-based approach to certify live-fire facilities for use with any variety of small arms ammunition can be applied.
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Induction hardening, a promising approach for selective hardening of metal parts, is widely used for surface hardening, where a hard surface is required alongside a tough core. Regarding the complexity of this process, parts’ geometry deeply affects the temperature distribution and hardness profile accordingly. In this study, two magnetic flux concentrators are introduced to our induction machine set in order to control the magnetic flux and consequently hardness profile (case depth) of spur gears. The performance of magnetic flux concentrators is examined by the effect of machine parameters on the case depth and the edge effect of AISI 4340 steel-made spur gear. Design of experiments based on Taguchi method is primarily used to optimize the number of experimental trials. Then, the hardness profiles of heat-treated gears at the tip and root of gears are measured by microindentation hardness tests. The results are analyzed using analysis of variance (ANOVA) and response surface methodology (RSM) to determine the main effect of process parameters, also the best combination of process parameters that maximizes the case depth and minimizes the undesirable feature of edge effect. Finally, the predicted case depth models versus process parameters are developed based on linear regression method. To this end, four predictive models of case depth at tip and root in the edge plane and middle plane of spur gears are generated. Results imply that maximum case depth with minimum edge effect at root and tip is achieved by setting up the highest machine power, longest heating time, and minimum axial gap between concentrators and the spur gear. This study provides a good exploration of case depth in presence of magnetic flux concentrators under various process parameters and gives a reliable guideline towards edge effect during induction hardening process.
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In this study, some physical properties of a laminated composite beam were estimated by using the inverse vibration problem method. Laminated composite plate was modeled and simulated to obtain vibration responses for different length-to-thickness ratios in ANSYS. A numerical model of the laminated composite beam with unknown parameters was also developed using a two-dimensional finite element model by utilizing the Euler-Bernoulli beam theory. Then, these two models were embedded into the optimization program to form the objective function to be minimized using genetic algorithms. After minimizing the squared difference of the natural frequencies from these two models, the unknown parameters of the laminated composite beam were found. It is observed in this study that the Euler-Bernoulli beam theory suppositions approximated the real results with a rate of %0.026 error as the thickness of the beam got thinner. The estimated values were finally compared with the expected values and a very good correspondence was observed.
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Pultrusion is one of the polymer composite fabrication processes employing a combination of pulling and extrusion processes. The composite profiles are obtained by pulling resin-impregnated fibres through a series of heated dies. The ability of the pultrusion technique to support a high volume of fibre fraction produces the high stiffness of the composite profile. There are many parameters such as filler loading, mould temperature and pulling speed to be considered and controlled during the pultrusion process. In this paper, an investigation of the effect of the filler loading on the tensile and flexural properties of the pultruded kenaf reinforced vinyl ester composites is presented. As the filler loadings were increased to a significant amount, the mechanical properties started to drop, which was attributed to the increase of viscosity in the matrix and in turn the increase in porosity and decrease in the wettability of the composites. Hence, increasing the amount of filler loading increased the tensile and flexural properties of the pultruded composites in terms of strength and stiffness. The tensile properties of the composites had increased by up to 50% of fibre loading. The maximum flexural strength and modulus were obtained at 30 and 50% of filler loadings respectively. The maximum compressive strength was observed to take place at 40% of filler loading.
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This study presents a free vibration analysis of a laminated composite beam, based on the Euler-Bernoulli beam theory. A numerical model of the laminated composite beam was obtained for various boundary conditions based on different length-to-thickness ratios for a number of layers, using the finite element method. A planar beam bending element with two nodes, each having two degrees of freedom, was chosen according to Euler-Bernoulli beam theory. The natural frequencies of the laminated composite beam were obtained for each case, and presented in such a way as to display the effect of these changes on the natural frequencies. Eight natural frequencies of clamped-free, clamped-clamped (CC) and simple-simple (SS) composite beams were first obtained for different length-to-thickness ratios (Lx /h), numbers of layers, layer angles and for their different positions. It can be seen that natural frequencies decrease for all modes with increasing length-to-thickness ratio in all cases.
This book covers the important issues of terminal ballistics in a comprehensive way combining experimental data, numerical simulations and analytical modeling. The first chapter reviews the experimental equipment which are used for ballistic tests and the diagnostics for material characterization under impulsive loading conditions. The second chapter covers essential features of the codes which are used for terminal ballistics such as the Euler vs. Lagrange schemes and meshing techniques, as well as the most popular material models. The third chapter, devoted to the penetration mechanics of rigid penetrators, brings the update of modeling in this field. The fourth chapter deals with plate perforation and the fifth chapter deals with the penetration mechanics of shaped charge jets and eroding long rods. The last two chapters discuss several techniques for the disruption and defeating of the main threats in armor design. Throughout the book the authors demonstrate the advantages of numerical simulations in understanding the basic physics behind the investigated phenomena.
Texture and microstructure development of Al-4Cu-1.6Mg alloy during hot rolling was examined by using XRD, EBSD and TEM. The results showed that starting with a random texture during the early stages of rolling with reduction lower than 58.9% at blooming temperature of 430 °C, the materials developed a typical α-fiber texture in the center layer as deformation reduction reached 75.7%. And then the α-fiber textures in the center layer rotated into Brass component mainly through the activity of {111}<110> slip system as the reduction reached 96.3%. Different from the center textures, the main texture in the surface layer was r-Cube with 96.3% reduction. The increase in rolling temperature was beneficial for the enhanced texture intensity of Brass component in the center layer. The analysis of substructure energy density indicated that Brass subgrain had a lower substructural energy density than other oriented subgrains, which together with increased slip rate at elevated temperature, contributed to the development of center Brass texture.
The high-temperature temper embrittlement of martensitic heat-resistant 10Cr12Ni steel was studied. The results demonstrate that there is some irreversible temper embrittlement when the steel is tempered at 625 °C. The irreversible temper embrittlement can be overcome by re-tempering at higher temperature. The tempered martensite embrittlement at 625 °C is attributed to the precipitation of M23C6-type carbides along the martensite lath and prior austenite grain boundaries. The tempering process can be divided into three stages: In the first stage, the martensite laths recover and M7C3-type carbides precipitate inside the martensite laths, leading to the improvement of the toughness. In the second stage, M7C3-type carbides dissolve, and M23C6-type carbides precipitate along the martensite laths and prior austenite grain boundaries. The M23C6-type carbides play a nucleating role in the development of cracks, leading to tempered martensite embrittlement. In the third stage, the toughness gradually recovers with the further recovery of the martensite laths.
A Rolled Homogeneous Armour (RHA) steel was tested at strain rates in excess of 103 s-1 in compression using direct impact Hopkinson Bar. The dynamic stress-strain curves and microstructural evolution in this material at high strain rates were obtained. They were found to be dependent on the extent of thermal softening occurring during deformation and the accompanying visco-plastic instabilities, which lead to localization of shear strain along adiabatic shear bands (ASBs). The formation and the type of shear bands are found to depend on the impact momentum and strain rates. Depending on the loading mode, there is a strain-rate threshold below which plastic deformation is homogeneous. At slightly higher strain rate, deformation becomes localized leading to formation of deformed ASBs. As impact momentum and strain rate increase, another threshold value is reached above which strain localization become so intense that it triggers the formation of transformed ASBs. Ductile shear fracture occurs along these transformed bands.
Low-alloy steels have been widely used as an armor material in defense systems due to their superior mechanical and weldability properties. In this study, microdamage formation in an AISI 4140 steel, which was hit by 7.62-mm armor-piercing (AP) projectile, was investigated. Analyses of the microstructure and microhardness after ballistic testing were performed to correlate the microstructure-property relationship. Two different types of adiabatic shear band (ASB) were observed in the tested samples. The experimental results indicated that the type and hardness of the bands were strongly related to the hardness and ballistic performance of the steel specimens.
Steels have been used for ballistic protection for a long time, a great deal of experience in their manufacturing and use has been acquired. Recent progress achieved at Creusot-Loire Industrie in ladle refining and in processing techniques has made it possible to develop new armored steels with improved ballistic performances. This paper presents the different types of armored steels: high-hardness homogeneous steels, multilayered armor and composite armor used for structural applications and for add-on-armor. The dynamic behavior of armored steels is described. A new approach to determining the relationship between metallurgical parameters and ballistic resistance is presented. It is shown how the study of dynamic characteristics, perforation mechanisms and modelling can help to develop new armors.