Mohamad S El-Zein

John Deere · Moline Technology and Innovation Center

Welding is one of the most widely used process for joining structural components in automotive, ship building, rail road, aerospace, construction, transportation and many other industrial applications. One of the common links for such applications is long term fatigue durability of the structures and most importantly the welded joints. Most failure...

Welded steel joints are widely used for the structural components in the on/off-highway industry. Due to increasing regulations around CO2 emissions and competitive demand for improved fuel economy, there is a significant focus on the lightweighting of structures in the machinery components deriving the use of higher strength steel grades. It’s giv...

Traditional manufacturing processes, like arc welding and resistance spot welding, are still the main welding processes to join structural components used across the on/off-road vehicle industry. Due to the abundance of data, experiences and insights over the decades of usage, lot of fatigue design data has been generated for different joint geomet...

With the increased use of adhesive joints in industrial environments, the need for improvement of this bonding technology arises. Namely, a reliable fatigue life estimation is essential to prevent catastrophic failure in adhesively bonded structural components. The cohesive zone model (CZM) approach has been used in numerical models to assess degra...

Residual stresses in welded joints are produced as a result of localized, complex and transient heat cycles from welding processes. These residual stresses are mostly undesired due to their tensile nature, especially near the weld toe where externally applied stress levels are raised due to geometric stress concentration. Tensile residual stress ca...

An experimentally validated fatigue model is proposed for the effect of mean stress on high-cycle fatigue performance of preloaded threaded fasteners. The proposed model is compared with commonly used models by Goodman, Gerber, Morrow, Soderberg, and ASME-Elliptic (ASME B106.1M:1985). Fatigue S-N curves are experimentally generated at various mean...

This book presents recent material science-based and mechanical analysis-based advances in joining processes. It includes all related processes, e.g. friction stir welding, joining by plastic deformation, laser welding, clinch joining, and adhesive bonding, as well as hybrid joints. It gathers selected full-length papers from the 1st Conference on...

The role that a materials engineer did and will be playing today and in the future is examined through a new outlook at function, education, training, project management, and collaboration. The need for this collaborative role through adjacencies’ knowledge is driven by the reliance of the industry on subject matter experts in light weighting, valu...

The aim of this paper is to investigate the fatigue fracture behavior of three different adhesive systems (epoxy‐based, acrylic, and a rubber‐like adhesive). To achieve this, double cantilever beam specimens were manufactured with different adhesives and tested under several mode mixities and different load levels. Fatigue crack growth rate was eva...

Depending on the expression used in Paris law relation, crack growth rate can be a function of loading conditions. However, for design purposes, it is costly and time consuming to obtain a complete map for fatigue crack growth behavior of adhesives. Accordingly, using a damage parameter where the Paris law constants are similar for different loadin...

Traditional manufacturing processes, like arc welding and resistance spot welding, are still the main welding processes to join structural components used across the on/off-road vehicle industry. Due to the abundance of data, experiences and insights over the decades of usage, lot of fatigue design data has been generated for different joint geomet...

Adhesive joints usually experience mixed mode and mostly cyclic stresses conditions during their service life. The aim of the current research is to investigate the fatigue behaviour of a structural epoxy adhesive. Pure modes I and II and mixed mode tests were carried out to study the fracture and fatigue crack growth (FCG) behaviour of the adhesiv...

http://2019.fatiguedurability.com/

State of the art fracture mechanics based UniGrow model with total life approach [1] has been successfully applied for fatigue life estimation of the arc and laser welded joints [2,3]. During this work an effort has been made to extend the application of this approach to predict the fatigue life of adhesive bonded joints. The proposed approach uses...

The lap shear joint is a very common design configuration, and has several drawbacks, including peel stress concentrations at the edge of the lap. This problem is exacerbated in assemblies with unbalanced adherend stiffness [1]. A low-cost assembly may include steel and glass fiber reinforced epoxy (GFRP). A quasi-isotropic laminate GFRP has an ela...

Because of maintenance issues, the concept of safe life is an important philosophy for designing adhesive joints where the service load is cyclic. However, this philosophy needs a tool to be able to estimate the total fatigue life. The objective of this study is to develop a numerical tool to predict the fatigue life of adhesive joints for pure mod...

The conventional joining methods like resistance spot welding and arc welding have several challenges during joining of thin sheets of high strength steel materials. One of the main challenges is that application of these joining methods may result in a severe distortion of welded structure. Therefore, laser welding process has emerged as an altern...

In the case of structural weldments, the procedure for estimating fatigue life requires information concerning geometry of the object, loads, and material. Detailed knowledge of stress fields in the critical regions of weldments is used to determine the fatigue life. The main theme of the research discussed in this paper is to provide details of th...

Fatigue analyses of weldments require detailed knowledge of the stress fields in critical regions. The stress information is subsequently used for finding high local stresses where fatigue cracks may initiate and for calculating stress intensity factors and fatigue crack growth. The method proposed enables the determination of the stress concentrat...

Industrial carburizing operations have been traditionally simulated for several decades by solving the diffusion equation. However, using this deterministic approach, it is difficult to capture batch-to-batch variations in the properties attributed to process and chemistry variations. In the current study, a probabilistic approach is used to captur...

Changes in welding sequence have high effects on welding distortion and production time. As the effects on cycle time are simply due to the distance travelled by the Heat Source, the influences of welding sequence on distortion are still not clearly defined. The goal of this paper is to build a model of the entire welding process to get deeper insi...

Two grades of case-hardenable low carbon steel, with tempered martensitic structure, were subjected to strain-controlled (imposed strains: 0.35~0.9%) fatigue tests. Though the samples did not contain large (> 1 micron) non-metallic inclusions, a range of 'Fatigue Failure Probabilities' (FFPs) were estimated. After the respective fatigue failures, d...

Two grades of Steel, with tempered martensitic structure, were used for fatigue tests. From such tests, samples were obtained with significant differences in the probability of fatigue failure. The latter was related to surface/sub-surface misorientation developments and developments in compressive residual stresses. A combination of glancing incid...

Industrial heat treatment operations are getting significantly driven by the carbon footprint and stringent quality metrics in addition to the cost competitiveness. As a consequence, the role of heat treatment process modeling has been expanded from design and analysis stage to process optimization and control. The present work showcases some of th...

Materials processing methods, such as welding, casting and heat treatment operations, are key to development of robust products. Due to the recent development in analytical tools as well as enhancements in computational capabilities, application of process modeling of materials processing has significantly advanced-from design and analysis to proce...

Induction hardening is an important heat treatment operation for a number of components, including shafts, crank-shafts, gears, and axles to improve wear and fatigue properties. These parts are widely used in automotive as well as off-highway vehicles. Induction hardening process comprises of two distinct steps, induction heating and quenching oper...

The potential of residual stress engineering for developing leaner, greener, and safer design is discussed. The technique can be successfully employed at the design stage in the transportation sector and creates significant value by reducing the product's weight, cost, and carbon footprint. It is possible to estimate the compressive residual stress...

The first papers on computational welding simulation were published in the 1970s when computers became commonplace in research environments. The models used were simple and used simple means for verification. Today's computational power has increased the complexity of both the weld models and the techniques for verification. This paper discusses th...

To solve the transient temperature field for a given welding problem, we seek a model equation for the convection coefficient as a function of temperature at a point on the surface of the structure being welded. The model equation contains 1 to 5 parameters. To estimate the parameter values that minimize the deviation between the transient temperat...

The transient displacement field caused by an arc weld was measured experimentally with an Aramis stereo-camera. The transient displacement field was also predicted using a computational weld mechanics program called VrWeld for ten different sets of model parameters. The objective was to identify the effect of model parameters on the deviation betw...

This chapter intends to develop a design process for service life prediction of machines and structures. As the design fatigue life of materials and machines is usually far beyond that of the duration of laboratory tests, a life prediction theory based on an accelerated characterization technique must be developed. The accelerated characterization...

A new approach to the prediction of tensile strength after impact is presented. The method is based on the premises that the stress concentration associated with the constraint of the undamaged material around the impacted region dominates the remaining strength calculation and that the physical parameter that enters the model should be the size an...

The notched tensile strength of composite laminates was examined. The behavior and prediction of unidirectional off-axis, angle ply, and [0/±θ]s laminates is discussed. It was found that good predictions for off-axis laminates can be obtained since the same failure mode occurs in such laminates. Similar results were also obtained for the [0/±θ]s la...

The influence of interfaces and interphases on the mechanical behavior of composite materials has been widely discussed in the literature, particularly in the last few years. Several books have been devoted to the subject. Despite this fact, the systematic rep resentation of the mechanics of this subject remains grossly incomplete, and because of t...

The strength of notched and impact damaged laminates was studied. The solution U for a plate containing an elliptic opening and inclusion was used as given by Lekhnitskii. The solution for the infinite plate, combined with laminate analysis to determine the ply stresses, and the average stress criterion proposed by Whitney and Nuismer were used to...

An equation for the strain energy release rate GI of a double cantilever beam (DCB) specimen for an anisotropic material is obtained. Results show that for an orthotropic material, the solution coincides with the isotropic one. However, for a more general anisotropic case, an additional term appears, which is a function of the crack length, the mat...

The strength of notched and impact damaged laminates was studied. The solution for a plate containing an elliptic opening and inclusion was used as given by Lekhnitskii. The solution for the infinite plate, combined with laminate analysis to determine the ply stresses, and the average stress criterion proposed by Whitney and Nuismer were used to pr...