Laser Processing of Ni-Based Superalloy Surfaces Susceptible to Stress Concentration

Reliable and resilient constructions are basic for ensuring the safety of various structures. The superalloys are used as constructive materials due to their superb mechanical properties and endurance. However, even these materials can have certain areas where the stress concentration is higher than expected, such as drilling holes, which are common in various structures that need additional enhancement. Surface laser modifications of the areas surrounding the holes drilled in Nimonic 263 sheets are done by pulsed picosecond and nanosecond Nd:YAG laser irradiations with pulse durations of 170 ps and ≤8 ns, respectively. Following the laser surface treatment, the effectiveness of the enhancement was analyzed by the microhardness test and the deformation test. The results show that the deformation and stress values are decreased by 25−40 percent, showing the improvement in the resilience to deformation. The Vickers microhardness test results indicate an improvement in the Nimonic 263 microhardness. The dimensions of the microcracks are higher for the untreated material in comparison to the laser-treated material.

Revision Of A Standard For The Test Of A Toilet-Incorporated Medical Electric Bed

We developed a toilet-incorporated electric medical bed for bedridden patients, in which a toilet basin, or a commode, is incorporated in the pelvic plate of an electric medical bed. A replaceable toilet seat is located in the mattress of the bed, and toilet basin was tightly attached on the pelvic plate the bed. The excretion slides through a storage tube that angles toward the side of the bed and is automatically collected in a disposable plastic bag. We, however, encountered a problem with testing this newly developed medical bed with the relevant international standard IEC 60601-2-52:2009, or with the corresponding Korean standard KS P 0388:2012--Electrically operated adjustable bed for home care. There was no clear indication in the scopes of the above standards as to whether this standard testing method is applicable to an electric medical bed embedded with a commode. We revised the Korean standard KS P 0388:2012 to accommodate the toilet-incorporated medical bed in the scope of the standard and successfully performed the mechanical tests including the durability, impact, and deformation test of the bed, proving that the newly developed toilet-incorporated medical bed is mechanically strong and durable enough to pass the standard tests.

Study on Radial Clearance Sealing Performance of Graphite Ring

Firstly, the suitable forming method of graphite ring was screened according to compression deformation test, considering the characteristics of radial clearance seal. Then, the compression resilience, radial contact stress and axial sealing performance of graphite packing rings with different density were researched by testing. Research shows: 25% compressibility is the limit of radial clearance compensation ability of graphite packing ring; And the radial contact stress of graphite packing ring on the pipe wall is linearly positively correlated with the axial load, density has little effect on it. Based on the porous media model of gaskets, axial leakage models of three kinds of graphite rings with different density were obtained by experimental fitting and the influence of external working conditions on leakage mode was analyzed, which provide a theoretical basis for the design of graphite ring seal based on leakage rate.

A new way to identify thin sheet behaviour: Micro-InDef

Incremental forming is a rapid prototyping process which uses a forming tool toform a sheet metal according to a predetermined trajectory. In this work, a micro incremental deformation test (Micro InDef test) derived from the principle of single point incremental sheet forming is developed and proposed. A complex mechanical loading is applied and has a strong potential for the identication of inelastic behavior using inverse method. In the rst part, this work addresses the parameters identication and validation procedures of ductile damage behavior of ultra-thin sheet metal under very large strain during this instrumented Micro InDef test. An inverse nite element method based on the comparison between numerical and experimental axial forming forces of the micro incremental deformation test is employed to extract a coupled ductile damaged plastic model. In the second part, the objective is to prove the reliability of ductile damage parameters identication using forming force. The richness of data contained in forming force is quantied and compared to the one from tensile test. Firstly, the verication of the estimated parameter's reliability is done via a simple analysis based on the forming force sensitivity to material parameters and secondly by calculating elastoplastic and elastoplastic with ductile damage.