Effect of T-stress on Fracture of a Long Cracked Plate in Unsteady Heat Transfer

In order to accurately predict the structure fracture caused by thermal load, a modified maximum tensile stress (MTS) criterion combined with T-stress is proposed. The modified MTS uses a two-parameter model (stress intensity factor K and T-stress) to describe the fracture behavior under thermal load. The T-stress and stress intensity factor at the crack tip are solved by using J-integral in the theoretical calculation of a cracked strip with temperature difference. The results show that T-stress can affect the fracture toughness and the stress at the crack tip of the cracked strip with temperature difference. This provides a basis for the simulation of structural fracture under thermal load.

Drilling Supporting Technology for Exploration and Development of A Marginal Oilfield

Marginal oil fields refer to some small and medium-sized oil fields or oil fields with complex stratigraphic structure and located in remote areas. There are more than 100 large and small blocks marginal oil fields with huge reserves. They have the characteristics of geological reservoirs such as structural fracture, fault development and complex oil reservoirs. The development is uncertain and is not suitable for excessive investment. How to carry out economic and effective exploration and development of marginal oil fields has become a new breakthrough in stabilizing production and improving benefits in A oilfield, as the first marginal oil field with “extended test of development evaluation wells + overall development plan”, designed and manufactured three hole asymmetric underwater wellhead base plate in combination with mudline hanger in order to meet the needs of overall oilfield development, Realize the temporary abandonment of the extended test well after the test, and put it back into production in the overall development stage of the oilfield. It provides a new mode of cost reduction and efficiency increase for the subsequent development of marginal oil fields, which will revitalize a large number of marginal oil fields to be developed and bring huge economic and social benefits. The establishment of a safe risk response mode of “advance can be attacked and retreat can be defended” can improve the efficiency of preliminary research and avoid the risk of oilfield development.

Polyethylene-Based Knee Spacer for Infection Control: Design Concept and Pre-Clinical In Vitro Validations

Antibiotic-loaded polymethyl methacrylate (PMMA) has been widely applied in the treatment of knee periprosthetic joint infections. However, problems with antibiotic-loaded PMMA-based spacers, such as structural fracture and implant dislocation, remain unresolved. A novel polyethylene-based spacer, designed with an ultra-congruent articulating surface and multiple fenestrations, was introduced in the current study. Validation tests for biomechanical safety, wear performance, and efficacy of antibiotic cement were reported. During cycle fatigue testing, no tibial spacer failures were observed, and less wear debris generation was reported compared to commercial PMMA-based spacers. The volumetric wear of the novel spacer was within the safety threshold for osteolysis-free volumetric wear. An effective infection control was demonstrated despite the application of lesser antibiotic cement in the 30-day antibiotic elution test. The tube dilution test confirmed adequate inhibitory capabilities against pathogens with the loaded antibiotic option utilized in the current study. The novel polyethylene-based knee spacer may offer sufficient biomechanical safety and serve as an adequate carrier of antibiotic-loaded cement for infection control. Further clinical trials shall be conducted for more comprehensive validation of the novel spacer for practical application.

Damage Boundary Study of Crystal Oscillators under Shock Environment

The crystal oscillator is a widely used electronic component in a circuit, whose accuracy is strongly affected by the external mechanical environment. To depict the failure mechanism of the crystal oscillator, the damage boundary of this component under the shock environment is studied experimentally in this paper. Through subjecting “step-up” loads on different groups of crystal oscillators, two failure modes (frequency jumping and structural fracture) are monitored and validated. Experimental results prove that “frequency jumping” failure mode is governed by the value of the acceleration shock response spectrum (ASRS) in a certain frequency range, while the failure mode “structural fracture” is governed by the peak value of the ASRS. Through analyzing the shock response spectrum, damage boundaries are given for these two failure modes, which can provide a reference for component design and failure assessment.

A Study of the Mechanical Properties of Au Nanomeshes

We study the mechanical behavior of Au nanomeshes (AuNMs) based on finite element analysis (FEA) simulation and deformation tests. The simulated results of mechanical flexibility indicate that polyethylene terephthalate (PET) substrate can release the stress of AuNMs under mechanical stretching and bending, the displacement of stretched AuNMs yields a 2% promotion, and the displacement of bent AuNMs yields a 3.5% promotion under buffering of PET substrate at 5 GPa yield strength of nanoscale Au. The stress and displacement distribution of the AuNMs/PET is demonstrated and analyzed. The further deformation tests of AuNMs under compressive and tensile loading indicate that the simulation data are in good agreement with experimental results. This paper is conducive to understanding the mechanical behavior and corresponding structural response and structural fracture dynamics of AuNMs.

Experimental Study of Strain-Softening Stage in Materials

Physical theory of reliability is based on research into degradation processes of various origins which take place in a material of a stressed construction. Experimental evaluation of parameters carried out for such processes is a practically important problem by itself. One of the approaches to solving this problem is related to the studies into the stage of material softening due to deformation. This paper analyzes the issues of experimental validation of material softening properties in terms of a phenomenological approach to the problem of structural fracture. Results of deformation analysis for the “machine – model specimen” system, using catastrophe theory are used to form requirements for carrying out experiments which investigate the softening stage of materials. The success of such experiments – which should include recording a branch descending to zero on a computer diagram – is possible when small specimen, made from structurally heterogeneous materials, are strained in a sufficiently rigid testing machine. Thus, the conditions for manifestation of the softening stage connect properties of the material with properties of the load-applying system. Therefore, the material's limiting state – preceding the fractured – also depends on the conditions of loading, and the criteria of that fracture would be nonlocal. In consideration of the results of diagrams plotted from various bases for deformation measurement, a necessity of utilizing local material characteristics for calculation purposes is discussed. As an example of using the complete diagrams for determining kinetics of material degradation from external load, the results of specimen testing, which follows a cyclic training, are cited.