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Argues that the dynamic‐explicit approach has in recent years been successfully applied to the solution of various quasi‐static, elastic‐plastic problems, especially in the metal forming area. A condition for the success has, however, been that the problems have been displacement‐driven. The solution of similar force‐driven problems, using this approach, has been shown to be much more complicated and computationally time consuming because of the difficulties in controlling the unphysical dynamic forces. Describes a project aiming to develop a methodology by which a force‐driven problem can be analysed with similar computational effort as a corresponding displacement‐driven one. To this end an adaptive loading procedure has been developed, in which the loading rate is controlled by a prescribed velocity norm. Presents several examples in order to exhibit the merits of the proposed procedure.

The aim of the present study is to find the tribological properties of newly developed polyester-based hybrid glass-jute fibre reinforced plastic composites loaded with different weight per cent of hybrid filler particles were investigated under a dry sliding medium from room temperature to 75°C.

The study was carried out using a pin-on-disc wear test set-up. The design of experiments was carried out in a controlled way using a central composite design based on response surface methodology to observe the effect of various parameters i.e. sliding velocity, sliding distance, the temperature of counterface and different applied load conditions during dry-sliding.

The maximum wear resistance was found at 9 Wt% loading of filler, 4 ms^-1 sliding velocity, 30 N applied load, 54°C temperature of the counterface and 1,100 m sliding distance condition. Optimum values of hybrid filler loading, sliding velocity, applied load, the temperature of the counterface and sliding distance for the minimum coefficient of friction value and minimum friction force are 9 Wt%, 4 ms⁻¹, 30 N, 54° C, 1,100 m and 12 Wt%, 3 ms⁻¹, 20 N, 59°C and 1,100 m, respectively. The worn surface morphology was studied using scanning electron microscope, for wear dominant mechanisms.

The tribological properties of newly developed polyester-based hybrid glass-jute fibre reinforced plastic composites loaded with different weight % of hybrid filler particles, were investigated under dry sliding medium from room temperature to 75°C has not been attempted yet.

The purpose of this paper is to introduce and analyze a new blast-wave impact-mitigation concept using advanced computational methods and tools. The concept involves the use of a protective structure consisting of bimolecular reactants displaying a number of critical characteristics, including: a high level of thermodynamic stability under ambient conditions (to ensure a long shelf-life of the protective structure); the capability to undergo fast/large-yield chemical reactions under blast-impact induced shock-loading conditions; large negative activation and reaction volumes to provide effective attenuation of the pressure-dominated shockwave stress field through the volumetric-energy storing effects; and a large activation energy for efficient energy dissipation. The case of a particular bimolecular chemical reaction involving polyvinyl pyridine and cyclohexyl chloride as reactants and polyvinyl pyridinium ionic salt as the reaction product is analyzed.

Direct simulations of single planar shockwave propagations through the reactive mixture are carried out, and the structure of the shock front examined, as a function of the occurrence of the chemical reaction. To properly capture the shockwave-induced initiation of the chemical reactions during an impact event, all the calculations carried out in the present work involved the use of all-atom molecular-level equilibrium and non-equilibrium reactive molecular-dynamics simulations. In other words, atomic bonding is not pre-assigned, but is rather determined dynamically and adaptively using the concepts of the bond order and atomic valence.

The results obtained clearly reveal that when the chemical reactions are allowed to take place at the shock front and in the shockwave, the resulting shock front undergoes a considerable level of dispersion. Consequently, the (conserved) linear momentum is transferred (during the interaction of the protective-structure borne shockwaves with the protected structure) to the protected structure over a longer time period, while the peak loading experienced by the protected structure is substantially reduced.

To the authors’ knowledge, the present work is the first attempt to simulate shock-induced chemical reactions at the molecular level, for purposes of blast-mitigation.

The aim of this paper is to investigate transverse impact behaviour and energy absorption of 3‐D glass/polyester resin cellular woven composite impacted by flat‐ended rod and to discuss the failure modes of the composite under quasi‐static and dynamic loading.

The quasi‐static compression tests were conducted with MTS 810.23 tester. The impact behaviours of the 3‐D cellular woven composite were tested with a modified split Hopkinson pressure bar (SHPB) apparatus.

Failure loads and energy absorption capacities of the 3‐D cellular woven composite increase as the increase of load speed, i.e. the composite is strain rate sensitive. The failure loads and energy absorptions in warp direction are lower than those in weft direction at the same loading speed because of the lower linear density of warp yarns. The damage morphologies of the 3‐D cellular woven composite manifest the compression failure in the front side and tension failure in rear side.

The influence of different structure parameters on the failure mode should be studied.

The study provided information on the failure mode and energy absorption of the 3‐D cellular woven composite under impulsive loading. This could be used for light weight structure design, such as vehicle and aircraft stringer structures.

Understanding energy absorption of the 3‐D cellular woven composite under transverse impact is much more important than those under quasi‐static loading. This paper provides the results of dynamic mechanical properties of a new kind of 3‐D cellular woven composite under impact loading.

The purpose of this paper is to find the response of micro‐layered rapid prototyping material under impact loading.

A modified Hopkinson Bar was used to impart impact loading in velocities ranging from 2‐7 m/s. Strain gages and stress wave theory were employed to calculate the load‐point force and displacement. Hence the dynamic crack initiation and propagation energies were calculated.

It was found that the crack deflection and inter layer delamination mechanisms lead to greater absorption of crack propagation energy and hence offer better resistance to crack propagation as compared to monolithic acrylonitrile butadiene styrene (ABS).

The finding will lead to greater confidence for the use of rapid prototypes as direct‐use parts subjected to low velocity impact.

Although the static properties of ABS material used in rapid prototyping are well documented, this paper is one of the first reported researches in measuring the impact response of the micro layered ABS.

The aim of this paper is to study the effect of pressure angle and helix angle on bending stress at the root of helical gear tooth under dynamic state. Gear design is a highly complex process. The consistent demand to build low-cost, quieter and efficient machinery has resulted in a gradual change in gear design. Gear parameters such as pressure angle, helix angle, etc. affect the load-carrying capacity of gear teeth. Adequate load-carrying capacity of a gear is a prime requirement. The failure at the critical section because of bending stress is an unavoidable phenomenon. Besides this fact, the extent of these failures can be reduced by a proper gear design. The stresses produced under dynamic loading conditions in machine member differ considerably from those produced under static loading.

The present work is intended to study the effect of pressure angle and helix angle on the bending stress at the root of helical gear tooth under dynamic state. The photostress method has been used as experimental methods. Theoretical analysis was carried out by velocity factor method and Spott’s equation. LS DYNA has been used for finite element (FE) analysis.

The results show that experimental method gives a bending stress value that is closer to the true value, and bending stress varies with pressure angle and helix angle. The photostress technique gives clear knowledge of stress pattern at root of tooth.

The outcomes of this work help the designer use optimum weight-to-torque ratio of gear; this is ultimately going to reduce the total bulk of the gear box.

This study aims to perform dynamic response analysis of damaged rigid-frame bridges under multiple moving loads using analytical based transfer matrix method (TMM). The effects of crack depth, moving load velocity and damping on the dynamic response of the model are discussed. The dynamic amplifications are investigated for various damage scenarios in addition to displacement time-histories.

Timoshenko beam theory (TBT) and Rayleigh-Love bar theory (RLBT) are used for bending and axial vibrations, respectively. The cracks are modeled using rotational and extensional springs. The structure is simplified into an equivalent single degree of freedom (SDOF) system using exact mode shapes to perform forced vibration analysis according to moving load convoy.

The results are compared to experimental data from literature for different damaged beam under moving load scenarios where a good agreement is observed. The proposed approach is also verified using the results from previous studies for free vibration analysis of cracked frames as well as dynamic response of cracked beams subjected to moving load. The importance of using TBT and RLBT instead of Euler–Bernoulli beam theory (EBT) and classical bar theory (CBT) is revealed. The results show that peak dynamic response at mid-span of the beam is more sensitive to crack length when compared to moving load velocity and damping properties.

The combination of TMM and modal superposition is presented for dynamic response analysis of damaged rigid-frame bridges subjected to moving convoy loading. The effectiveness of transfer matrix formulations for the free vibration analysis of this model shows that proposed approach may be extended to free and forced vibration analysis of more complicated structures such as rigid-frame bridges supported by piles and having multiple cracks.

AT THE INTERNATIONAL CONFERENCE ON GEARING arranged by the Institution of Mechanical Engineers in London from the 23rd to 25th September, a special session was set aside for the Discussion of Lubrication and the following papers were presented :—

The piston ring-cylinder liner pair is one of the most important tribological systems of an internal combustion engine. The friction loss of the piston ring-cylinder liner pair accounts for the largest portion of total efficiency losses. Therefore, improving the tribological system design of the piston ring-cylinder liner pair can reduce friction losses and bring tremendous economic benefits to society. This paper aims use surface texturing, which is proving to be an effective method, for improving the tribological performance of sliding surfaces.

In this paper, an experimental study using a pin-on-disk tribometer was carried out to evaluate the effects of surface texturing on friction reduction of piston rings under various loads and sliding velocities. Rectangular- and circular-shaped textures with different depths and area densities were produced by a Femtosecond laser. Comparison experiments were conducted with un-textured rings.

The results indicate that the friction performance of the ring surface was significantly improved by surface texturing, and the running-in stage was also shortened. More specifically, it was found that the rectangular-shaped texture had a better effect on friction reduction than the circular-shaped texture. Results also indicate that an optimum texture density existed for the rectangular-shaped texture. Additionally, it was observed that the average friction coefficient reduction of the textured ring decreased with increasing load and increased with increasing sliding velocity.

Consequently, these findings provide a more in-depth understanding of the relationship between micro-textures and tribological properties of piston rings in lubricating sliding.

The properties of materials under impact load are introduced in terms of metal, nonmetallic materials and composite materials. And the application of impact load research in biological fields is also mentioned. The current hot research topics and achievements in this field are summarized. In addition, some problems in theoretical modeling and testing of the mechanical properties of materials are discussed.

The situation of materials under impact load is of great significance to show the mechanical performance. The performance of various materials under impact load is different, and there are many research methods. It is affected by some kinds of factors, such as the temperature, the gap and the speed of load.

The research on mechanical properties of materials under impact load has the characteristics as fellow. It is difficult to build the theoretical model, verify by experiment and analyze the data accumulation.

This review provides a reference for further study of material properties.