Experimental study on lapping ceramic balls with variable-radius groove plate

The method of lapping precision ball with variable-radius groove is developed in recent years. An experimental study on lapping ceramic balls with variable-radius groove was carried out. Taguchi method was used to design the orthogonal experiment of rough lapping, and the material removal rate ( MRR) and the roundness were selected as evaluation indicators. The signal to noise ratio (S/N) and the analysis of variance were used to analyze experimental results. The optimal parameters combination with load pressure of 2.5 N/Ball, abrasive concentration of 10 wt% and rotation speed of 15 rpm was obtained. During rough lapping, the maximum reduction rate of average roundness is 50%, the maximum reduction rate of roundness deviation is 81%, the MRR is 16.9 μm/h, and the reduction rate of variation of ball lot diameter ( VDWL) is 90%. After semi-lapping and polishing, the best surface roughness is up to 10 nm, the best roundness is 0.128 μm, and the VDWL is 0.24 μm. The surface roughness and VDWL of the five balls tested all meet the requirements of ceramic ball with G5 grade, and the roundness value is close to the requirement of G5. The variable-radius groove lapping method is very suitable for improving the precision of batch lapping for ceramic balls.

p-harmonic functions by way of intrinsic mean value properties

Let Ω be a bounded domain in ℝ n {\mathbb{R}^{n}} . Under appropriate conditions on Ω, we prove existence and uniqueness of continuous functions solving the Dirichlet problem associated to certain nonlinear mean value properties in Ω with respect to balls of variable radius. We also show that, when properly normalized, such functions converge to the p-harmonic solution of the Dirichlet problem in Ω for p ⩾ 2 {p\geqslant 2} . Existence is obtained via iteration, a fundamental tool being the construction of explicit universal barriers in Ω.

Dynamic Modeling and Simulation of a Robotic Lander Based on Variable Radius Drums

Soft-landing on planetary surfaces is the main challenge in most space exploration missions. In this work, the dynamic modeling and simulation of a three-legged robotic lander based on variable radius drums are presented. In particular, the proposed robotic system consists of a non-reversible mechanism that allows a landing object to constant decelerate in the phase of impact with ground. The mechanism is based on variable radius drums, which are used to shape the elastic response of a spring to produce a specific behavior. A dynamic model of the proposed robotic lander is first presented. Then, its behavior is evaluated through numerical multibody simulations. Results show the feasibility of the proposed design and applicability of the mechanism in landing operations.